Most homes, businesses, and other dwellings have some type of heating system which includes some sort of heating system that is safely shutdown should the heater flame be lost or inadequate for continued safe and efficient operation. There are several methods of sensing flame in a combustion based heating system such as, for example, various light spectrum sensors, sensors of conducted heat, and sensors of ionized gaseous products of combustion. Light spectrum sensors generally detect a specific range of frequencies within the electromagnetic spectrum such as infrared, visible light and ultraviolet light. Proper detection of flame requires that the radiation detected correlates with the presence of flame—and only flame. A drawback with visible and infrared sensors is that they usually detect the afterglow of the fuel combustion chamber—in addition to flame—so as to be imprecise in determining when flame is lost. Another drawback with visible spectrum light detection involves its tendency to pick up stray ambient light. Yet another drawback with visible and infrared sensing of flame is a comparatively poor detection of flames from combusting gaseous fuel.
Ultraviolet (UV) flame sensors have broader application without the above-mentioned drawbacks with infrared and visible light sensors. However, most UV sensors used for flame sensing have the drawbacks of high operating voltages, and nonlinear correlation of signal generated to flame intensity received. The high operating voltage requires more expensive safety protection measures. The nonlinear flame to signal correlation requires more complex signal manipulation and analysis, which usually results in greater expense and reduced accuracy.
Conventional heating systems generally are periodically tuned by skilled personnel, either as needed, or on a predetermined schedule (typically annually). The ‘as needed’ conditions generally involve a response to an obvious malfunctioning of the heating system by the end user of this heating equipment. This mode of malfunction detection is usually very erratic, involves detection most often by unskilled observers, and frequently results in heating equipment needing extensive servicing. Periodic scheduled servicing is generally done annually. Most often, however, the average heating system receives this scheduled service more frequently than is necessary for continued safe and efficient operation. This equates to excessive service expense.
Another aspect to conventional combustible fuel based heating systems involves the need to periodically replenish the fuel for continued operation. Conventional procedures for fuel replenishment generally involve either delivery-on-demand by the personnel overseeing the heating system, or, more often, by estimations by the fuel dealer of when the specific heating system will be needing additional fuel. The later estimates are usually based on the history of the particular heating system, along with analysis of probable fuel usage based on the record of daily outdoor temperatures. These fuel usage estimates are usually very inaccurate (typically about 25% in error). Additionally, the negative effects of having a customer run out of fuel, coupled with this inaccurate usage estimation procedure combine to motivate fuel dealers to factor in a significant margin of remaining customer fuel at the time of delivery. This equates to more frequent deliveries of fuel than desirable, resulting in greater fuel delivery expense.